Influence of Posture on Skin and Subcutaneous Temperatures

Abstract

Previous experiments 1 showed that the cardiac output in the sitting and standing positions was less than in the recumbent. They also indicated the probability that the former positions facilitate the return of a disproportionately large amount of blood from the short systemic circuits, although the amount from the extremities and the splanchnic area is decreased. The present report deals with observations on blood flow, particularly in the extremities, as measured by surface and subcutaneous temperatures.

Eight adult subjects with normal cardiovascular systems have been systematically studied. Temperatures in various parts of the body were determined by means of surface and non-conducting hypodermic thermocouples in a potentiometric circuit so arranged as to permit rapid and accurate consecutive readings. 2 The subcutaneous thermocouples were inserted to a depth of from 2 to 4 mm. Passive change of position from the horizontal to an angle of 75 degrees was achieved by a tilt table, the subject being held in place by supports over the iliac crests. This method of support eliminated the necessity of a foot-rest, objectionable because of the tendency of subjects to carry and shift enough weight on their lower extremities to aid in the venous return through muscle action. The subjects remained at 75 degrees for from 14 to 40 min, being returned to the horizontal position when they complained of being uncomfortable or became faint. Room temperature was maintained relatively constant during each experiment by means of fans and heaters.

A typical experiment is charted in Figure 1. In addition to the usual surface to subcutaneous temperature gradient, both temperatures showed gradients from toes to forehead when the subjects were in the horizontal position. When tilted to 75 degrees, there was, in general, a progressive decrease in the temperatures of all parts of the (body measured, (being most marked in the extremities. The lowest values were usually reached at the end of the tilt period, or within one to three minutes after the return to the horizontal in those instances where the tilt period was terminated by fainting. In the majority of the experiments the temperatures returned to or were approaching their original levels in from 15 to 60 min after the subjects were returned to the horizontal position.